Hey @WebTreeSoftwareSolut and @Cris.MntYetti,
we do experience some flakiness (especially with apex domains). Often the cause is that the domain is registered with Cloudflare and there is some misconfiguration.
When you use Cloudflare, you need to make sure that you have disable edge certificates as it can interfere with the custom domains service. You can disable it the following way: Go to your domain in the cloudflare panel, then go to “SSL/TLS” → “Edge Certificates”, scroll all the way down and “Disable Universal SSL”. After you have done that, you can start the process again.
Are you both using Cloudflare?